Selective two pitch airscrew



May 20, 1941- G. ALGARSSON SELECTIVE rwo PITCH AIRSCREW Filed Jan. 16, 1939 6 Sheets-Sheet 1 INVENTOR GRETTIR ALsARssoN I B M ATTQRNEXU May 20, 1941. G. ALGARSSON 2,243,046

I SELECTIVE TWO PITCH AIRSCREW Filed Jan. 16, 1939 6 Sheets-Sheet 3 ROTATION OF A Amscgzew K w pmzH OslTlON 7 LNVENTOR GRETTIR ALsARssoN BY W ATTORNEY May 20, 19 1- G. ALGARSSON SELECTIVE TWO PITCH A IRSCREW Filed Jaxi. 16, 1939 6 Sheets-$heet 4 QOTAT! ON .OF

4 Amscyzew PITCH-CHANGKNG PosmoN XNVENTQR GRETTIR ALsARssoN \/4 I M/ B V M ATTORNEY y 20, 1941- G. ALGARSSON 2,243,046

SELECTIVE TWO PITCH AIRSCREW Fi l ed Jan. 16,- 1939 e Sheets-Sheet 5 ROTATION OF AHQECREW K HIGH PITCH POSITION mvENToR GRETTIR ALGARSSON ATTORNEY May 20, 1941. G. ALGARSSON 2,243,045 I SELECTIVE TWO PITCH AIRSCREW Filed Jan. 16, 1959 e Sheets-Sheet s mvENToR GRETTIR ,ALeARssoN pail/71M BY ATTORNEY Patented May 20, 1941 SELECTIVE TWO PITCH AIRSCREW Grettir Algarsson, Montreal, Quebec, Canada Application January 16, 1939, Serial No. 251,109

, 11 Claims. (01. 170-162) This invention relates to selective two pitch airscrews as described in the present specification and illustrated in the accompanying drawings that form part of the same.

The invention consists essentially in the utilization of the torque reaction of the airscrew to alter the pitch of the blades, as pointed out in the claims for novelty following a description in detail of an acceptable form of the invention.

The objects of the invention are: to take advantage of the natural tendency of the airscrew to lag behind or overrun the engine, this tendency being utilized to vary the pitch setting of the airscrew blades; to place the selection of the pitch within the control of the pilot without adding to the number of controls; to render impossible change of pitch of the blades to high pitch setting at low speeds or to low pitch setting at high speeds of the aircraft; to eliminate all control connections to the airscrew; to provide improved takeofi and permit the efficient development and use of the power available at low airspeeds; to provide a mechanism applicable to standard equipment without alteration thereof; to reduce the number of working parts, thereby simplifying manufacture and upkeep; to permit axial penetration of the airscrew hub thus facilitating installation of a gun, firing through the hub; and generally to increase the efllciency of the aircraft by permitting heavier takeoff loads and increased speeds.

According to the invention an airscrew is provided in which a low pitch and a high pitch setting are available. The changes from low pitch to high pitch and vice versa depend in part upon control of the pilot and may be delayed indefinitely if desired.

When it is desired to change pitch, all that is necessary is to slow down the engine, allowing the airscrew to overrun the engine for an instant. When this occurs the pitch changing mechanism unlocks, permitting the airscrew to change pitch, if the speed of the aircraft is such as to warrant a change of pitch. As long as the engine is driving the airscrew the mechanism is locked, and no change of pitch can occur until the pilot causes the airscrew to overrun the engine.

In the preferred form of the invention, described in detail hereinafter, the hub casing, in which the blades are mounted, is permitted a limited rotation with respect to the mounting sleeve which is keyed or splincd to the engine crankshaft in the same manner as a fixed pitch airscrew. Journal blocks, carried by the mounting sleeve, engage with pitch levers, attached to the blade roots, causing the blades to change pitch as the hub casing rotates with respect to the mounting sleeve. Stop surfaces on the mounting sleeve, transmit the torque of the engine'to corresponding stop surfaces on the hub casing,

either directly, holding the blades in low pitch,.

the hub, and are extracted from between the stop' surfaces by the pressure of springs which overcome-the pressure on the disc when the speed of the aircraft is below the selected value.

Referring to the drawings,

Figure 1 is a side elevation of an'airscrew hub of the preferred variety.

Figure 2 is a sectional front elevation on the line 2-2 of Figure 1, with-the spring cartridges removed.

Figure 3 is a sectional side elevation corre-' sponding to Figure 1.

Figure 4 is a sectional view of a spring cartridge.

Figure 5 is a sectional front elevation on the.

line 5-5 of Figure 1.

Figure 6 is a diagrammatic side elevation of the hub illustrated in the previous figures, showing the relative positions of the mounting sleeve,

hub casing, blades and spacers in position.

Figure 7 is a sectional front elevation on the line ll of Figure 6.

the low pitch Figure 8 is a diagrammatic planshowing the pitch setting of the upper blade in Figure 7.

Figure 9 is a diagrammatic side elevation corresponding to Figure 6, but showing the relative positions of the various parts in the pitch changing position. The dotted lines show the spacers in the inward position.

Figure 10 is a sectional front elevation on the line Ill-i0 of Figure 9.

Figure 11 is a diagrammatic plan showing the I pitch setting of the upper blade in Figure 10.

Figure 12 is a diagrammatic side elevation corresponding to Figure 6, but showing the relative positions of the various parts in the high pitch position.

Figure 13 is a sectional front elevation on the line I3-l3 of Figure 12.

Figure 14 is a diagrammatic plan showing the pitch setting of the upper blade in Figure 13.

'2 T g I aaeao-ro diagrammatic [side elevation of 7 ball bearings 40 and the adjustment washers 4| athreeblader'f-airscrew showing therelative posi- I are the root sleeves 42. The. blades 43 are tions 'of' the mounting'sleeve, hub casing, blades "-'=mounted in the root sleeves in any suitable and spacers infthe. pitch-changing position. manner. I

Figure 16 is a sectional front elevation on the 5 A central link 44 passes around the mounting line IG"I6 ofFiE J e 15.

Figure 17 is a. front elevation of the hub shown ball bearings 45 which take the centrifugal pull in Figures 1 and 2. of the blades 43 and root sleeves 42 through the The airscrew hereinafter described is composed pins 48. The pins 46 are screw-threaded into the of parts which'may be classified in three groups. 10 root sleeves with a buttress thread, designed to First, that do not move in relation to the take a maximum of tensile load with a minimum engine crankshaft. of resultant bursting stress upon the root sleeve,

Second, parts'that move in relation to the first and are locked against unscrewing by the ends group as theairscrew blades change pitch. of the pitch levers 41 which enter the holes 8, Third, parts that move in relation to the first drilled in the .pins 43 after tightening up on the and second groups in cooperation with the aneinner races of the ball bearin s mometric disc. The pitch levers 41 are rigidly mounted in the The engine crankshaft, to which the parts clasroot sleeves 42, being accurately fitted into holes sleeve, but does not bear upon it, housing the sified in the first group are rigidly attached, i drilled in the bases of the blade roots and screwdesignated by the numeral [5. The crankshaft threaded into them near the ends which look the It has a. tapered end terminating in a threaded ns 'h t h l vers are lo ked against unportion to receive the retaining nut is. screwing y the lock pins 43 which are held in The mounting sleeve I1 is kept on the crankplace by-the split pins 50 at the outward ends of I shaft 1| 5, by the retaining nut 16 and held against the pitch levers 41.

relativei: rotation by the key l8. 5 The ssembly consisting of h n mot Int estal im t mounting sleeve n is t sleeves, central link bearings, pins and pitch torquefplate l9 which-has a rectangular orifice 20 levers cannot come apart in any particular so long "near the root of each blade., At the outside and as the split P ns 50 remain in P .insi deQrespectively, of the orifices 2 0 are the If the adjustment washers II are of the right caps 2i and 22 whichare attached to the so thickness e ades will be correctly mounted on torque plate by the flat head machine screws the h esingand the ball bearings wand 45 gq w that; velastic; vstop nuts g4 will all simultaneously receive the correct amount -'Ihe spacer guide studs 25 are screw-thread d of pre-load.- Substitution of adjustment washers .m fi u plate 9 and are prevented-from 4| will correct inaccuracies in pre-load and also an y; the comers of t bearing caps provides a means of roughly balancing the blades, "whicharereoessed into the flanges 26 which precise balance being achieved by varying the he te'gral-with the guide studs. The stop nuts amount of lead held in the undercut holes 5|.

he orward movement of the third group I in the hub casing. These orifices are so shaped d on to the rear end of 5 34;! that the pitch levers can move freely, withthe th bearing adjustment ring "bladesg through the maximum pitch range that "n its correct positlon,by means could be required. The outer ends of the pitch igk-wbefore the mounting ev r I 5a through the orifices 20 in the torque I "and are connected with the latter by men. of the-journal pieces 53 and the journal blocks 54 jI'he journal blocks 54 have project'- inglfstub axles 55 which are attached to the torque ,jplat'e by the bearing caps H and 22 in such a manner a to'permit rotation about and a limited Csirigfarethe torque stops 32 on'w l novementalon'g the axes of their stub axles. ustinentflbars stare; mounted by m a P" .m 1 Pieces whmh are drilled I {the a t g m screws}; thee ceive the pitch levers l1, arecarried by the v 'mmt u :5 Journal blocks 54 in such a manner as to per- Y adjustmentfbars are the plane f 'mit angular change between the pitch levers and of the torque plate} I9and,- consequentlmjfi the'stub axles 1 'g t u n ft hub ca ing m ns t When the stop surfaces 36 are in contact with I the-mounting sleeve. Stop surfaces '36 and 31. the stop surfaces the rq e plate I9 is in a on the torque plate. l9 and the adjustment hers definlte ti n in relation to the hub casing 33, respectively, provide ample bearing surfaceto" 3 fi-S the or ue of e engine driving he airtransmit the-engine torque from the torque-plate screw is transmitted h h hese stop surfaces, t t u s n they will be held in this relative position. As the t e t urface 33 and 39 on th t r u pitchlevers'are mounted ri idly in the root sleeves as'ufisgthez nuh casing 3|.

j The pitch levers pass through the orifices 52 plate and tm t bars respectively, limit i 2, but connectedtowards their 0111281" ends Wlfll relative rotation of the hub casing in'the'opp tte' eto que plate, the airsc blades re eld in direction and provide bearingsurfaces to trans-v an W K SP WU P s n the qu mit the torque of the airscrew to the engine-when 91W?v s q i relation to the hub casing,

the former tends to overrun the l tter. It will eparatin the stop surfaces 36 d he outer be observed that the engine is assumed to have ends, f e pit h levers must" move with it in reright-hand rotation, as indicated.by.1'arrows .in' a latlonto the :hub'ca'sing which carries: the root t various flgure5 7o sleeves, thusjlncreasing the pitch of the blades The spacers 56, which will be described in'de- 1 1 S nc ease of pitch is arrestedjby contail hereafter, are insertable between the stop tact between the stop surfaces 38 von the torque surfaces 36 on the torque plate'N-and'the'stop pate and the stop surfaces 39 on the adjustsurfaces 31 on the adjustment bars 33.

- fitment barsr v I Carried on the hub casi1 1g 3-l. byr'means ofithe It will thus be seen that the hub casing, carin tligtortiiie plate.

The third. group of. parts, those moving fin, relatiori tofthev tlr'stf'andfsecbnd grbups in cooperationwith the anemornetric. dug-consists of .;the spacers together i withthe a'nerriormtricv disc and springs which control their movement in and out between the stop surfacesiixand 31,- when' these latter are separated owing to theairscrew tending to overrun the engine. a

The'spacers 56, which, herr -interposed between the stop surfaces 36 and I1; hold the airscrew blades in. the high pitch position, are in tegral-"with the spacer ring 51 (see Figure 6), which is-mounted on the spacer guide studs 25. The spacer ring 51 is provided with lugs 58 (see Figure 1) on its inward side through which machine screws 59 are fastened-by. means of elastic stop nuts. Spring cartridges 60 are journalled at one end on the machine screws I which are fastened through lugs 82. on the torque plate by means of other elastic stop nuts. Referring tof.

Figure it will be seen that each spring comprises two closed ended cylinders 63 and lt, one slidably mounted withinthe other, contaim -JMWK' the arrangement of the pitchleverslmoulit'e in. the blade roots and the journal blocks mounted.-

rem-Stan 11.1

'51, ,angle increases as the .movesinwardsagainst the springsg ct the pressure orv the springs. and the wholegroup .of parts commences tomove inwards the h g p h p s fii na. hem which 'e priests are ntemseepepw shop spring artridges? er. ca germ I angle-to thel lineofemovement. i

quen' of this'fchang e'ofangl a, i v I sure-onthedisc 68 produces an increasingg pressure againsti' -the springs. The "springsare so designed that their pressure, as they are "com'- pressed,.'does not increase as rapidly .as the corresponding resultant of a constant pressure upon thedisc"- I The effect-of thisarrangement is that once the parts. omposingthe third group start'to move nward-under aerodynamic pressure-on the disc, *theyfinimediatelyitravel the whole distance, being opposed by adecreasing resistance, 1. e., they ing a compression spring, exerting pressure}.

tending to separate the cylinders, thereby length ening the cartridge. Mounted in ,frontzof' the spacer ring by means of the metallic bracingbolts. 66 and the bracing tube 61 is the anemometric disc 68.

The spacers are provided with bevelled steps 69;-

which fit into correspondingly bevelled depres-" sions 10 in the adjustment bars 33 when the airscrew is in the high pitch setting.

Referring to the drawings it will be understood that, so long as the engine is transmitting torque to the airscrew, the stop surfaces 36 and 3.1 will be in contact, unless they are held apart by the spacers 56. T ere are, therefore, two pitch positions or settings available while the engine is driving the airscrew. The low pitch position is that in which the stop surfaces 38 and 31 are in direct contact, and the high pitch position is that in which the spacers are held between the stop surfaces.

While in the low pitch position, the spacers staiit for the fraction of a trip the mechanism).

' The-third group of. parts will hereinafter be referred toas the trip mechanism.

' In :the operation of the airscrew as a whole,

truly-This tripping action also occurs in the opposite" direction; when "changing from high pitchto .low, owing to the fact that. the spring -pressureydoes not decrease as rapidlyas the opposing-resultant of the pressure on the disc (which' latter; may be considered as being consecond required to the actual operation of changing pitch is accomplished :by causing the'airscrew to overrun the engine, thereby turning the blades into the. extreme high pitch or pitch-changing position, and "then causing the engine to drive the airscrew,

thu turning the blades to as low a pitch as the stop surfaces 36 and 31 (which transmit the torque of the engine to the airscrew blades) will permit. The functionof the trip mechanism is to separate the stop surfaces by the thickness of 4 the spacers, thereby holding the blades in high cannot enter between the stop surfaces. and.

while in the high pitch position the spacers are locked in place by the bevelled steps 59 and".

A third pitch position is assumed wh'enthe stop surfaces 38 and 39 are in contact, 1. e., when the airscrew overruns the engine; This is the pitchchanging position and is slightly higher than the high pitch position, the stop surfaces. 38' and 31 being sufficiently far apart to permit the spacers to enter or withdraw from between the stop sur-.

faces in response to the action of the third of parts.

The operation of the third group of parts is as follows:

The spacer ring 51, together with the spacers 56, bracing bolts 66, bracing tube 61 and anemornetric disc 68, is held in the outward or low pitch position, against the aerodynamic pressure upon the disc 68, by the compression springs 65 operating within the spring cartridges 60. As the speed of the aircraft increases,. the aerodynamic pressure upon the disc 68 increases, until ,a speed is reached at which the pressure upon the disc group pitch, if the speed of the aircraft is high enough eusethe mechanism to .mwardi of to allow the stop 'suriaces'to come togetherfthereby permitting the-engine-to turn menace into low pitch. ,1 the speed of the air: enough toicause' the mechanism- Ward.

The thickness of the spacers, therefore, deter; mines thepitchrange or difierence betweenlow and high xpitch, main will be understood that.

substitutio' of adjustment bars 33 of varying thickness' atithe' surface 31 will vary thelow pitch position;

Substitution. bracingbolts and tubes of air". ferent lengths. rmltafiy required adjustment of the distance betweenthe. front of-theairscrew hub and ,thedisc .58.: and. changing the-;$i ze of the disc .or thei' strength of the springs will vary.

the pressure required toftripi l-the ,trip mechanism, thereby varying the "critical" speed of the aircraft, 1. e., the speed at which change ofpitch canbe accomplished.

Considering the operation of the airscrew during an imaginary flight. During the takeoffv the airscrew will be in low pitch and will remain in low pitch until the critical speed is reached.

Once the airspeed has risen abovethe critical value, the pilot canv change tohigh pitch at any moment he selects, but the airscrew" will notchange to high pitch until the pilot closes the throttle to the required extent. Once inhigh m netism.

pitch, the airscrew will remain there until the I airspeed has fallen below the critical value and even then will not return to low pitch unless pilot makes the required movement of the throttle.

The foregoing description applies specifically to" I the form of the invention illustrated in the figures including the three blades airscrew shown" in Figures and 16,

Many other forms however, could be used without going beyond the 'scope' of the invention.

For instance, the arrangement of the 'trip mechanism could be varied, or the torque plate could be placed behind the hub instead of in front, thus causing the engine torque to turn the blades .to high pitch, and usingthe-spacers to hold the blades in low pitch, etc. i

a In all its forms, however, it may be seenthat the selective .two pitch airscrew which is the subject of this application, is one that can be changed from lowpitch tohigh pitch or vice versa at. the will of the pilot, but isjproot against accidental or mistaken changes into high pitchat m Iowan speed or into low pitch attoo high an airspeed.

What I claim is: y

1. In a two pitch airscrew, a drivenmounting sleeve, a hub casing so mounted on said sleeve as to permit rotation thereon and provide one lim-": i-ting position when the driven sleeve isimpart ing torque to the airscrew'and another limiting position when the airscrew overruns the'driven' sleeve, blades rotatablymounted in the hub cas-x ing, means causing the blades to rotate in the hub casing as the casing rotates on the sleeve, spacers insertable when the airscrew overruns the driven sleeve, changing the limit of rotation and pitch setting of the airscrew when the driven .sleeve is again imparting torque to theairscrew,

sleeve engaging with the stops on the hub casing and providing one limiting position when the driven sleeve is imparting torque to the airscrew and another limiting position when-the airscrew overruns the driven sleeve, blades rotatably 'mounted in the hub casing, means causing 'the blades to rotate in the hub casing as the casing rotates on the sleeve, spacers'insertablebetween the stops when the airscrew overruns the drivensleeve, changing the limit of rotation and pitch setting of the airscrew when the driven sleeve'is' again imparting torque to the airscrew, and

means actuated by aerodynamic pressure c'o'ntrolling the insertion or extraction of the spacers and the pitch setting of the airscrew. v

3. In a two pitch airscrew, a m'ounting'sleeve,

a hub casing journalled on said sleeve, stops on the hub casing, stops on the sleeve engaging with the stops on the hub casing and limiting itsrot'ation with respect to the sleeve, spacersinsertable between the stops on the hub casing and the stops on the sleeve, blades rotatably mounted in the hub casing, means connecting the blades a hub casing journalied on said sleeve, stops on the'hub casing, stops on the sleeve'engaging with the stops on the 'hubcasing and limiting its rotation with respect to the sleeve, adjustment bars secured to said stops to adjust the limits of said rotation,- spacers insertable between the stops on the 'hub' casing and the stepson the sleeve,

, and hub casing 5. In a two pitch airscrew, a mountingsleeve, a torque plate integral with said sleeve, a hub casing rotatably mdunted on the sleeve, stops on the torque plate and on the hub casing limiting their relative rotation, blades rotatably mounted on the hub casing, means causing the blades to change pitch in agreement with relative rotation of the hub casing and sleeve, spacers insertable between the stops on the torque plate and those on the hub casing, said spacers, when inserted, narrowing the limits of relative rotation between the hub'casing and the sleeve, andmeans including a disc supported against the pressure of the airstream' by springs, said means causing the on the hub casing limiting their relative rotation,

blades rotatably mounted on the hub casing, means causing the blades to change pitch in agreement withrelative rotation of the hub casing and sleeve, spacers insertable between the stops on the torque plate and those on the hub casing, said spacers, when inserted, narrowing the limits of, relative rotation between the hub casing and the sleeve, and means including a disc supported against the pressure of the airstream by springs, said means causing the spacers to trip inward interposing between the stops as the disc moves outward under pressure of the springs and to trip outward escaping from between the stops as the disc moves inwardunder aerodynamic pressure.

7. In atwo pitch airscrew, a mounting sleeve, a torque plate integral with saidsleeve, ahub casingrotatably mounted on said sleeve behind the torque plate, stops on the torque plate and on the hub casing limiting their relative rotation,- blades rotatably mounted on the hub casing, means causing the blades tov change pitch-in agreement with relative rotation of the hub casing and sleeve, spacers insertable between the 1 stops on the torque plate, and those on the hub casing, said spacers, when inserted, narrowing the limits of relative rotation between the hub casing and'the sleeve, and means including a disc supported against the pressure of the airstream by'springs, said means causing the spacers to trip inward interposing between the stops as with the sleeve causing the former to rotate as the latter rotates in relation to the hub casing,

and means including a disc supported against the pressure of the airstream by springs con trolling the insertion of the spacers between the stops on the sleeve and hub casing.

4. In a two pitch airscrew, a mounting sleeve,

the-disc moves inward under aerodynamic pressure and to trip outward escaping from between the stops as the disc moves outward'under pressure of the springs,

8. In a two pitch airscrew, a mounting sleeve, a torque plate integral with said sleeve, a hub casing rotatably mounted on said sleeve in front of the torque plate, stops on the torque plate and on the hub casing limiting their relative rotation, blades rotatably mounted on the hub casing, means causing the blades to change pitch in agreement with relative rotation of the hub casing and sleeve, spacers insertable between the stops on the torque plate and those on the hub casing, said spacers, when inserted, narrowing the limits of relative rotation between the hub casing and the sleeve, and means including a disc supported against the pressure of the airstream by springs, said means causing the spacers to trip inward interposing between the stops as the disc moves outward under pressure of the springs and to trip outward escaping from between the stops as the disc moves inward under aerodynamic pressure, said spacers having bevelled projections engaging with correspondingly bevelled recesses in the surfaces of the stops against which they bear when inserted between the stops.

9. In a two pitch airscrew, a mounting sleeve, a torque plate integral with said sleeve, a hub casing rotatably mounted on said sleeve behind the torque plate, stops on the torque plate and on the hub casing limiting their relative rotation, blades rotatably mounted on the hub casing, means causing the blades to change pitch in agreement with relative rotation of ,the hub casing and sleeve, spacers insertable between the stops on the torque plate and those on the hub casing, said spacers, when inserted, narrowing the limits of relative rotation between the hub casing and the sleeve, and means including a disc supported against the pressure of the airstream by springs, said means causing the spacers to trip inward interposing between the stops as the disc moves inward under aerodynamic pressure and to trip outward escaping from between the stops as the disc moves outward under pressure of the springs, said spacers having bevelled projections engaging with correspondingly bevelled recesses in the surfaces of the stops against which they bear when inserted between the stops.

10. In a two pitch airscrew, a mounting sleeve, a torque-plate integral with said sleeve, a hub casing rotatably mounted on the sleeve, stops on the torque plate and on the. hub casing limiting their relative rotation, blades rotatably mounted on the hub casing, a central link passing around the sleeve and rotatably attached to the roots of the blades, means causing the blades to change pitch in agreement with relative rotation of the hub casing and sleeve, spacers insertable between the stops on the torque plate and those on the hub casing, said spacers, when inserted, narrowing the limits of relative rotation between the hub casing and the sleeve, and means including a disc supported against the pressure of the airstream by springs, said means causing the spacers to trip inwards or outwards in agreement with variations in aerodynamic pressure on the disc.

11. In a two pitch airscrew, a mounting sleeve, a torque plate integral with said sleeve, a hub casing journalled on the sleeve, stops on the hub casing engaging with corresponding stops on the torque plate to limit the rotation of the hub casing on the sleeve, blades rotatably mounted in the hub casing, a lever secured to the root of each blade extending radially therefrom, a journal piece journalled on each lever, a journal block engaging with each journal piece and so mounted on the torque plate as to cause rotation of the blade as the hub casing rotates in relation to the torque plate, spacers insertable between the stops on the hub casing and the stops on the torque plate when the hub casing and blades have overrun the mounting sleeve to the limit of relative rotation permitted, a disc mounted in front of the airscrew exposed to the airstream, springs opposing inward movement of the disc under pressure of the airstream, means connecting said disc with said springs causing the disc to trip inwards or outwards when the pressure in either direction starts it moving. and means to insert and extract the spacers in agreement with movement of the disc.

GRETIIR ALGARSSON. 

